An explosion in the Pakistani city of Quetta killed dozens of people shortly after polls opened in national elections that have been marred by allegations of pre-poll rigging.
The July 25 vote pits opposition leader Imran Khan's Tehreek-e-Insaf party (PTI) against jailed former Prime Minister Nawaz Sharif's Pakistan Muslim League-Nawaz (PML-N) party.
Pakistani security and health officials said at least 28 people were killed and 35 wounded in a blast targeting a police convoy in Quetta, the provincial capital of Balochistan Province. The explosion struck near a polling station that has since been closed.
The Islamic State (IS) extremist group claimed responsibility for the attack. The group said the attack was carried out by a suicide bomber, but did not provide further details or evidence for its claim.
Earlier this month, IS militants claimed responsibility for a suicide attack that killed 149 people at an election rally in the town of Mastung in Balochistan.
Earlier, an exchange of gunfire at a polling station in the Swabi district in northwestern Pakistan left one PTI party activist dead and four people injured. Police told RFE/RL that shots were exchanged between PTI and Awami National Party supporters and identified the killed victim as 30-year-old Shah Zeb.
Polls show a tight race, with Khan's party ahead in one survey with 30 percent, compared to 27 percent for PML-N, the outgoing ruling party. Sharif's party leads another poll with 26 percent compared to 25 percent for Khan's PTI.
In third place is the Pakistan People's Party (PPP) of Bilawal Bhutto Zardari, 29, the son of former Prime Minister Benazir Bhutto, who was assassinated in 2007. The PPP could emerge as a coalition kingmaker if no party wins a majority, as many experts expect.
"Our predictions are very murky right now," said Bilal Gilani, executive director of Gallup Pakistan, adding that a huge chunk of voters remain undecided. "It's still up for grabs."
Almost 106 million voters are eligible to cast ballots for the 342-member National Assembly, or the lower house of parliament, and assemblies in Khyber Pakhtunkhwa, Punjab, Sindh, and Balochistan provinces.
Sixty seats in the National Assembly are reserved specifically for women, and 10 for non-Muslim minorities.
Early results are expected late July 25, with the final result due on July 26.
The vote marks only the second time in Pakistan’s 70-year history that a civilian government has completed a full term and handed over to another civilian administration through the ballot box.
Pakistan's military has ruled for approximately half the period since the country’s independence in 1947, staging coups three times.
The campaign has been characterized by "blatant, aggressive and unabashed attempts to manipulate" the outcome, with a crackdown on the media and the intimidation of candidates, according to Pakistan's Independent Human Rights Commission.
At the center of most allegations is the powerful military establishment, which has an oversized role in the country's domestic and foreign affairs.
The PML-N has alleged pre-poll rigging and accused the army of influencing the judiciary to deny it a second term.
Former premier Sharif was sentenced to 10 years in prison on corruption charges in absentia. He was arrested after returning to Pakistan on July 13 and has appealed his sentence.
Sharif, a vocal critic of the army, was dismissed from office by the Supreme Court in July 2017 for allegedly concealing assets abroad and other corruption allegations. He denies any wrongdoing.
Allies of the three-time prime minister, whose previous term ended when he was toppled in a military coup in 1999, have called the proceedings against him a political vendetta and suggested the army might be behind it.
Sharif has accused the army of paving the way for Khan, which the former cricket star denies.
The campaign also has been marked by violence, with a string of militant attacks killing more than 180 people, including three candidates.
The military has stationed over 370,000 personnel nationwide to ensure the vote goes smoothly -- the largest such deployment in Pakistan's history on an election day. An additional 450,000 police have also been assigned to provide security.
An unprecedented number of extremist religious parties also are participating in the election, including some that have been banned but are running under new names.
Political parties held their final rallies on July 23 before campaigning was suspended.
"I am giving this task to all of you to wake up early on the 25th and cast your vote," Khan told supporters in the eastern city of Lahore.
PML-N leader and brother of the former premier Shahbaz Sharif said victory was "certain."
"Despite all the odds PML-N is winning the July 25 polls," he was quoted as saying by Pakistani media.
With reporting by Reuters, AP, AFP, and Dawn